1. Field of the Invention
The present invention relates to a check valve actuator and more particularly to a check valve actuator that quickly and safely opens a check valve to allow as substance under pressure such as natural gas to flow through the check valve.
2. Description of Related Art
With reference to FIG. 5, a conventional check valve actuator (70) is tubular and has a body (71), a drive shaft (72), a pushrod (73), a discharge fitting (74), a knob (75) and a mounting collar (76).
The body (71) is hollow and has a front end, a rear end, a top, an internal cavity and a discharge port. The discharge port is formed in the top of the body (71) and communicates with the internal cavity.
The drive shaft (72) extends rotatably through the internal cavity from the rear end to the front end of the body (71) and has an outer end, an inner end and an external thread. The external thread is formed around the outer end of the drive shaft (72).
The pushrod (73) is connected to the inner end of the drive shaft (72), selectively protrudes from the front end of the body (71) to press a check valve disk away from a corresponding check valve seat to open the check valve and has an outer end and an inner end. The outer end of the pushrod (73) is attached to the inner end of the drive shaft (72) inside the body (71).
The discharge fitting (74) is tubular and is mounted in the discharge port in the body (71).
The knob (75) is mounted on the outer end of the drive shaft (72) near the rear end of the body (71), selectively extends or retracts the drive shaft (72) from the front end of the body (71) and has a center and a threaded hole. The threaded hole is formed in the center of the knob (75) and screws onto the external thread on the drive shaft (72). When the knob (75) is turned to extend the drive shaft (72), the pushrod (73) presses the check valve disk away from the check valve seat and allow a substance to flow through the check valve and the internal cavity of the body (71) and discharge fitting (74) of the conventional check valve actuator (70). When the knob (75) is turned to retract the drive shaft (72), the pushrod (73) pulls away from the check valve disk, and the check valve closes and stops the substance from flowing.
The mounting collar (76) is cylindrical, is attached to and protrudes longitudinally from the front end of the body (71) around the pushrod (73) and is mounted around a discharge port on a check valve.
However, the check valve actuator (70) has the following defects and shortcomings.
1. To keep the substance from leaking to the atmosphere, the knob (75) must be turned many times to extend and retract the pushrod (73), and this is time-consuming and trouble.
2. The pushrod (73) striking the disk may damage the check valve.